Everyone was doing it and the government was practically demanding it because a) they'd told everyone that real estate is the only asset class that never goes down, so keep buying and b) everyone should have a home, whether they can afford it or not, so make it happen banks, we'll even help.
So what law was broken exactly that these bankers should go to jail for? I have no doubt they've been investigated.
You want to know who should go to jail? Anyone selling student loans right now. That's going to blow up just as hard as the housing market did, and--in hindsight--their business practices will look just as shady. The equivalent of "How was a janitor going to afford a $300,000 house?" will be "How was an English lit major going to afford a $300,000 student loan?" The answer is "They can't" and I think you're a piece of shit if your job is to say otherwise. But when I say they should go to jail, I say so facetiously; they're not breaking any laws.